The present invention relates to hand held drilling and/or hammering tools powered by an electric motor. In particular the present invention relates to such tools in which the longitudinal axis of the motor is at an angle, generally substantially perpendicular, to the longitudinal axis of a drilling and/or hammering spindle of the tool.
Such tools mostly require the motor to be cooled by some means. Generally an airflow is generated by a fan mounted on the armature of the tool. When the armature of the motor rotates the fan is rotationally driven to generate an airflow. A casing of the motor is generally formed with an opening at the end of the motor remote from the fan, through which air can enter. Thus, when the fan rotates it pulls air into the opening and over the motor components. This air is then pulled into the fan and expelled by the fan and exits the motor casing via air outlets adjacent the fan. The type of fans used can be axial or radial fans, although radial fans are preferred due to the higher pressure they can generate. It is desirable that the motor cooling airflow is not expelled from the tool housing in an area of the tool housing, which, during use of the tool, may be directed towards the face of the user of the tool. This is because dust may be entrained in the airflow expelled from the tool housing.
For efficient running of the motor and improved lifetime of the motor it is preferred that the fan is fitted to the armature of the motor, before the motor sub-assembly is balanced. The balancing process ensures that the mass of the motor sub-assembly components is distributed evenly about the longitudinal axis of the motor. If conventional motor manufacturing plant is used, this means that the fan has to be fitted to the end of the motor remote from the commutator end of the motor. If the fan is located at the commutator end of the motor then it cannot be fitted before the motor is balanced, using conventional motor manufacturing equipment.
In so-called L-shaped drilling and/or hammering tools in which the motor is at an angle (generally perpendicular) to the axis of the drilling and or hammering spindle, the commutator end of the motor is the end located remote from the spindle. Thus, in L-shaped hammers, for the fan to be balanced, it must be located at the end of the motor adjacent to the spindle. This means that the motor cooling air is pulled into the motor at its end remote from the spindle and expelled from the motor at its end adjacent to the spindle. Expelling the motor cooling air flow from the spindle region of the tool is likely to lead to air being directed towards the face of a user of the tool during use of the tool.
This problem has been overcome in the past by locating a radial fan at the end of the motor adjacent to the commutator, after the motor sub-assembly has been balanced. This generates an airflow, which is expelled from the motor housing adjacent to the end of the motor remote from the spindle. Expelling air from this part of the tool housing directs the air away from the user's face in practically all-working positions of the tool. However, without balancing the average lifetime of the motor is reduced.